• Journal of the Korea institute for structural maintenance and inspection
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• v.20 no.1
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• pp.18-24
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• 2016

The purpose of this study is to induce the ductile behavior of the Ultra High Perfomance Concrete Reinforced I beam by substituting the part of steel fiber for bundle of reinforcing bars. Experiment of flexural behavior of the Ultra High Performance Concrete I shaped beam with the combination of the steel fiber and bundle of reinforcement bars was carried out. The volume fractions of steel fiber are 0%, 0.7%, 1%, 2%. The bundle of reinforcing bars and prestressing wire are used to restrain the concrete in compression zone. Length of bundle of reinforcing bar and prestressing wire is the one of test factors. The 9 Reinforced UHPC I shaped beam were made with these test factors. Not only steel fiber but also bundle of longitudinal reinforcing bar has effect to induce the ductile behavior of Reinforced UHPC I beam. The combination of 0.7% or 1.0% steel fiber and bundle of reinforcing bar showed the effective ductile behavior of I beam. The relationship of load-deflection and the crack pattern indicate the usefulness of the bundle of the longitudinal bar which has small diameter with close arrangement each other.

• Journal of Aerospace System Engineering
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• v.14 no.2
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• pp.28-35
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• 2020

In this paper, we present a design for a retraction-type actuator (ReACT) that has the characteristics of both thermomechanical metamaterials and displacement amplification mechanisms. The ReACT consists of an actuating bar, a diamond-shaped displacement amplification (DA) structure, and a slot for loading thin-film heaters formed through the actuating bar. When power is supplied to the thin film heater, the actuating bars contacting the heater thermally expand, and the diamond-shaped DA structures retract in the longitudinal direction. The performance characteristics of the ReACT, such as temperature distribution and retracting displacement, were calculated with thermomechanical analysis methods using the finite element method (FEM). Subsequently, the ReACTs were fabricated using a polymer-based 3D printer that can easily execute complex structures, and the performance of the ReACT was evaluated through repeated tests under various temperature conditions. The results of the performance evaluation were compared with the results of the FEM analysis.

• Journal of Korea Foundry Society
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• v.16 no.2
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• pp.116-123
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• 1996

The equipment for the horizontal continuous casting was built to produce hyper-eutectic Al-Si bars with a small cross-section of 25mm in diameter. The manufacturing processes including withdrawal cycle and secondary cooling methods were modified to refine the primary and the eutectic Si. The longitudinal casting speeds varied over the ranges of 670-1100mm/min for pure Al, and 200-350mm/min for Al-17wt%Si alloy. Due to the difference of cooling rate in the mould, microstructural asymmetry between the lower and the upper part of bar was observed. Thus, manufacturing processes such as cooling and withdrawal method were optimally combinated to get the homogeneous cast structure. With the increase of casting speed, the primary Si size was refined down to $30{\mu}m$ near the surface, and $80{\mu}m$ in the center of the bar.

• Advanced Composite Materials
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• v.16 no.2
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• pp.167-180
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• 2007

The tensile strength of unidirectional carbon fiber reinforced plastics under a high strain rate was experimentally investigated. A high-strain-rate test was performed using the tension-type split Hopkinson bar technique. In order to obtain the tensile stress-strain relations, a special fixture was used for the impact tensile specimen. The experimental results demonstrated that the tensile modulus and strength in the longitudinal direction are independent of the strain rate. In contrast, the tensile properties in the transverse direction and the shear properties increase with the strain rate. Moreover, it was observed that the strain-rate dependence of the shear strength is much stronger than that of the transverse strength. The tensile strength of off-axis specimens was measured using an oblique tab, and the experimental results were compared with the tensile strength predicted based on the Tsai-Hill failure criterion. It was concluded that the tensile strength can be characterized quite well using the above failure criterion under dynamic loading conditions.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.11a
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• pp.136-139
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• 2003

The re-bar work in the construction of nuclear power plants is difficult, due to the large diameter and the congestion of reinforcements. The mechanical anchorage offers a potential solution for this problem. However, the requirements or the standards for the shape of anchor plate of mechanical anchor has not been clearly established up to now. In this paper, the required performance of the mechanical anchorage for large diameter reinforcements in nuclear power plants are proposed, and the anchor plates are designed through nonlinear finite element analysis. The diameters of anchor plate are determined to be $\sqrt{5}$ times of reinforcement diameter for longitudinal reinforcements and $\sqrt{10}$ for shear reinforcements. The thickness of anchor plates is optimized as 0.3-0.35 times of reinforcement diameter for longitudinal reinforcements and 0.5~0.56 times for shear reinforcements.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07b
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• pp.728-731
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• 2003

This paper deals with a flat type ultrasonic motor, which uses a longitudinal-bending multi mode vibrator of rectangular form. A linear ultrasonic motor was designed by combination of the first longitudinal and eighth bending mode, and the motor consisted of a straight aluminum alloy bar bonded with piezoelectric ceramic elements as a driving element. The geometrical dimensions of the rectangular aluminum vibrator were determined by Euler-Bernoulli theory ANSYS was used to analyze the resonance frequency and the displacement of the stator vibrator. The resonance frequency of the motor provides the elliptical motion. and ANSYS was used to analyze elliptical motion and elliptical trajectory of stator vibrator when thickness of piezoelectric ceramics was varied respectively 0.763, 1.526, 2.289[mm] and width of stator vibrator was varied respectively 16, 12, 8, 4[mm]. When thickness of piezoelectric ceramics was decreased, the displacement of the stator vibrator was increased. And when width of stator vibrator was decreased, the displacement of the stator vibrator was increased.

• Journal of Sensor Science and Technology
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• v.18 no.2
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• pp.139-146
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• 2009

A Multilayered microelectrode design is presented for large area travelling wave dielectrophoresis (TwDEP) separators. Most of typical TwDEP chip has been arrayed with 1000 electrodes in $20{\times}20\;mm^2$. However, there is a limitation of the device area that is critical in throughput, because when the area of TwDEP becomes larger, the resistance of microelectrodes for bus bar is also increased. In this paper, we successfully developed a novel TwDEP chip with extremely large area ($31{\times}25\;mm^2$) by a unique multilayered bus bar design. According to the resistance simulation of our microelectrodes, it is possible to realize a TwDEP chip with an infinite longitudinal length. We demonstrated the feasibility of our suggestion with latex microbeads and showed the potential of extremely high throughput separation with TwDEP technique.

• Journal of the Earthquake Engineering Society of Korea
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• v.7 no.5
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• pp.25-35
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• 2003

Scale model tests were performed to investigate the seismic behavior of the solid and hollow rectangular RC piers with 50% of lap-spliced longitudinal bars in plastic hinge regions. Continuous bars and lap-spliced ones with a lap length of 39 times the bar diameter were arranged alternately in the sections. In order to clarify the influence of lap splice on a ductility the effect of axial force and lateral confinement were excluded in the test. The typical flexural failure conducting a ductile behavior were observed in both models. It is confirmed that the 50% of lap-spliced bars can be considered as an alternative of seismic detailing for longitudinal bars.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.8
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• pp.793-799
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• 2015

In this research, we study the propagation of longitudinal and transverse waves through a metal rod including a liquid layer using computational and experimental analyses. The propagation characteristics of longitudinal and transverse waves obtained by the computational and experimental analyses were consistent with the wave propagation theory for both cases, that is, the homogeneous metal rod and the metal rod including a liquid layer. The fluid-structure interaction modeling technique developed for the computational wave propagation analysis in this research can be applied to the more complex structures including solid-liquid interfaces.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.11a
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• pp.356-359
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• 2003

This paper deals with a flat type ultrasonic motor, which uses a longitudinal-bending multi mode vibrator of rectangular form. This ultrasonic motor was designed by combination of the first longitudinal and eighth bending mode, and the motor consisted of a straight aluminum alloy bar bonded with piezoelectric ceramic elements as a driving element. The geometrical dimensions of the rectangular aluminum vibrator were determined by Euler-Bernoulli theory In the experimental device, piezoelectric ceramics ( a piece of ceramic for the L-mode, $24\;{\times}\;8\;{\times}\;1[mm]$, and four pieces for the B-mode, $12.5\;{\times}\;8\;{\times}\;1[mm]$) were attached to one side of a aluminum plate($100\;{\times}\;8\;{\times}\;1[mm]$), and the stator was supported with a plastic case. As results, no-load rpm was 50[rev./m] when applied voltage was 150[Vrms] at the resonance frequency, and as the voltage was increased, the rpm was increased.